Book

Description:

Input:

Each test contains multiple test cases. The first line contains the number of test cases $$$t$$$ ($$$1 \le t \le 2\cdot10^4$$$).

The first line of each test case contains a single integer $$$n$$$ ($$$1 \le n \le 2\cdot10^5$$$) — number of chapters.

Then $$$n$$$ lines follow. The $$$i$$$-th line begins with an integer $$$k_i$$$ ($$$0 \le k_i \le n-1$$$) — number of chapters required to understand the $$$i$$$-th chapter. Then $$$k_i$$$ integers $$$a_{i,1}, a_{i,2}, \dots, a_{i, k_i}$$$ ($$$1 \le a_{i, j} \le n, a_{i, j} \ne i, a_{i, j} \ne a_{i, l}$$$ for $$$j \ne l$$$) follow — the chapters required to understand the $$$i$$$-th chapter.

It is guaranteed that the sum of $$$n$$$ and sum of $$$k_i$$$ over all testcases do not exceed $$$2\cdot10^5$$$.

Output:

For each test case, if the entire book can be understood, print how many times you will read it, otherwise print $$$-1$$$.

Sample Input:

5
4
1 2
0
2 1 4
1 2
5
1 5
1 1
1 2
1 3
1 4
5
0
0
2 1 2
1 2
2 2 1
4
2 2 3
0
0
2 3 2
5
1 2
1 3
1 4
1 5
0

Sample Output:

2
-1
1
2
5

Note:

In the first example, we will understand chapters $$$\{2, 4\}$$$ in the first reading and chapters $$$\{1, 3\}$$$ in the second reading of the book.

In the second example, every chapter requires the understanding of some other chapter, so it is impossible to understand the book.

In the third example, every chapter requires only chapters that appear earlier in the book, so we can understand everything in one go.

In the fourth example, we will understand chapters $$$\{2, 3, 4\}$$$ in the first reading and chapter $$$1$$$ in the second reading of the book.

In the fifth example, we will understand one chapter in every reading from $$$5$$$ to $$$1$$$.